Wolfenhold is home of the Worgen, though.
Technically, according to WoWWiki, Worgen are actually from another dimension and not on the world of Xoroth. The world of Xoroth is the homeworld of the Nathrezim and present in the same dimension as that of Azeroth. The name Wolfenhold certainly suggests that there would be worgen there, but there is no lore mention of such a location. So it really is a toss up between Worgen and Nathrezim although I'm leaning towards Worgen as it is under the "Planes set". So far, Bliz has brought in new races that are both familiar and new. BE from Azeroth and Draeni from Outland/Argus for BC, I'm thinking Pandarens from Azeroth and Worgen from another plane of exsistance.
Where are Pandaren closer to the Horde? As far as I knew they were mercenary heroes in WC3.
Go back to WCIII and play the Rexxar campaigns, they show the rapport between the Brewmaster Chen Stormstout and Rexxar. Chen's barrels are also scattered throughout the Barrens and leads to a quest that only the Horde can acquire. This leads to the hypothesis that the Horde are at least marginally closer to the Pandarens then the Alliance.
Interesting. I wonder where the story is headed with all of this. We're already killing off some of the big baddies and it's still relatively early on in script.
There are still plenty of baddies to be defeated. For the Maelstrom set, you'll probably see Queen Azshara in her Naga form as a raid boss along with another form of Hakkar (seeing as how there is Zandalar) and possibly someone who has discovered the other powers in the corpse of Sargeras in his Tomb within the Broken Isles.
In the Planes set, I suspect maybe a deranged Malfurion Stormrage, possibly Ysera The Sleeper (misguided like Malygos in Northrend), and the Elemental Lords imprisoned in the Elemental plane by the Titans: Ragnaros the Firelord(in his true, fully powered form), Therazane the Stonemother,Al'Akir the Windlord , and Neptulon the Tidehunter.
Finally in the Legion set, I'm thinking Kil'jaeden's full body not sticking out of a Sunwell, Some remaining Dreadlords (Balnazzar resuced and revitalized?), perhaps a corrupted Titan, and most definitely a restored Sargeras.